Comparative Evaluation of Central Corneal Thickness in Cross-Linked Keratoconic Eyes

Abstract

Purpose: To compare the central corneal thickness (CCT) measurements measured by using the Pentacam Scheimpflug system with the CCT measured using ultrasound pachymetry (UP) and to compare the compatibility between the methods in normal, keratoconic, and cross-linked keratoconic corneas. Methods: The study included 50 eyes of 50 patients with keratoconus (keratoconus group), 50 eyes of 50 patients with progressive keratoconus who underwent corneal cross-linking treatment (CCL group), and 50 eyes of 50 healthy subjects (control group). Patients in the keratoconus and CCL groups were further classified into mild (mean keratometry [Km] ≤ 47 D) and moderate keratoconus subgroups (47.0 < Km < 52.0 D). CCT values were noted from the Pentacam Scheimpflug and UP. Results: The difference between the Pentacam and UP values was largest in the CCL group (−20.9 0.21.5 μm), followed by the keratoconus and control groups (−10.6 0.20.3 and 0.4 0.6.8 μm). The Pentacam and UP measurements were not comparable in the keratoconus and CCL groups (P = 0.001 and P < 0.001), whereas they were comparable in the control group (P = 0.62). In subgroup analysis, the 2 methods were comparable in the mild keratoconus subgroup (P = 0.12) and not comparable in the moderate keratoconus subgroup and in both mild and moderate subgroups of the CCL group (P = 0.001, P < 0.001 and P < 0.001). Conclusions: Pentacam Scheimpflug tomography and UP can be used interchangeably in normal and mild keratoconic eyes, but not in moderate keratoconic and cross-linked keratoconic eyes. Pachymetry measurements from Scheimpflug must be interpreted with extreme caution with different methods before planning an invasive procedure in these eyes.

Long Term Evaluation of Posterior Corneal Surface Parameters after Accelerated Corneal Crosslinking with a Comparison with Uncross-Linked Keratoconic Eyes

“…Corneal thickness was measured thinner in the cross-linked group than in the progressive uncross-linked group despite a atter anterior surface. In a recent study by the current authors, the CCT measurement difference between the Pentacam and ultrasound pachymetry was largest in the CCL group, followed by the keratoconus and control groups (-20.9 ± 21.5, -10.6 ± 20.3, and 0.4 ± 6.8 µm), and it was concluded that pachymetric measurements from Scheimp ug must be interpreted with extreme caution [19].…”

Evaluation of Corneal Tomographic, Densitometric and Aberrometric Features Following Accelerated Corneal Cross-Linking in progressive keratoconus

“…The physiology of this corneal thinning after CCL still not identi ed: however, structural changes occur in corneal collagen brils (28), such as changes in corneal hydration (29), compression of collagen brils (30), edema (31), and keratocyte apoptosis (31) are discussed in the literature. It should be borne in mind that previous studies have that due to the difference between the Pentacam and ultrasound pachymetry, pachymetric values obtained from Pentacam printout should be interpreted with extreme discretion (32).…”

Evaluation of Corneal Tomographic, Densitometric, and Aberrometric Features Following Accelerated Corneal Cross-Linking in progressive keratoconus

“…The physiology of this corneal thinning after CCL is still not identi ed: however, structural changes occur in corneal collagen brils (28), such as changes in corneal hydration (29), compression of collagen brils (30), edema (31), and keratocyte apoptosis (31) are discussed in the literature. It should be borne in mind that previous studies have shown that due to the difference between the Pentacam and ultrasound pachymetry, pachymetric values obtained from Pentacam printout should be interpreted with extreme discretion (32).…”